This invention relates to an improved fluid driven motor and an associated telemetry system for transmitting data from one location to another. The invention is in certain respects especially useful as adapted to a down hole well drilling motor and a telemetry system for transmitting information from an instrument within a well to the surface of the earth, and will be described primarily as applied to that use.
Most directional drilling of oil or gas wells or the like is performed with drilling units including a motor which is lowered into the well at the bottom of a drill string and acts to drive a connected bit without rotation of the upper part of the string above the motor. A bent sub is connected into the string above the drilling unit to deflect it slightly laterally for attaining the desired directional drilling effect. In most instances, the motor is driven by the pressure of circulating fluid or mud which is pumped downwardly through the drill string and after passing through the motor is discharged at the bit to carry cuttings upwardly about the outside of the string.
Mud motors of this type are subject to a very rapid wear as a result of their continual contact with the highly abrasive circulating fluid which drives the motor, and consequently such a motor can only operate for relatively short period of time before it must be removed from the well and overhauled or replaced.
With regard to prior telemetry systems, the most common method of transmitting information from a steering tool, surveying tool, or other instrument located within a well has been by lowering the instrument into the well on a wire line and conducting electrical signals upwardly to the surface through that line. Such use of a wire line is for many reasons very inconvenient and expensive, and involves substantial losses in rig time in raising and lowering the instrument each time a pipe section is added to the drill string. Other telemetry systems utilized in wells have included arrangements in which electrical signals have been transmitted to the earth through the metal of a drill string and/or the surrounding earth formation, or have been converted to variations in pressure of the circulating fluid with those variations being controlled by the down hole instrument and being sensed at the surface of the earth.